Effects of Hydrogen Bonding on Diffusion of Aromatic Compounds in Acetone: An Experimental Investigation from 268.2 to 328.2 K.

Abstract

Diffusion coefficients of pseudoplanar aromatic compounds at infinite dilution in acetone have been measured at different temperatures by the Taylor dispersion technique. The data of the polar solutes that can form hydrogen bonds with acetone are compared with those of the nonpolar ones incapable of hydrogen bonding to quantify the effects of hydrogen-bonded association on diffusion. The effects are further found to correlate strongly with the overall hydrogen-bonded acidity of the polar solutes containing proton-donating groups. For the nonpolar solutes in this study, the diffusivities at different temperatures can be expressed very well by the recently developed molecular-modified fractional Stokes-Einstein relation with only two constants. An innovative model for solute diffusion in liquid solutions, which is constructed by combining the molecular-hydrodynamic relation for nonpolar solutes with the overall hydrogen-bonded acidity scale for polar solutes, is introduced for representing the diffusivities of different types of disc-shaped molecules at various temperatures. An equation developed from this model is demonstrated to be capable of calculating a total of 191 diffusion data of both the hydrogen-bonded and the nonassociated aromatic solutes in acetone from 268.2 to 328.2 K to a standard deviation of 2.7%.